LOLBAS/yml/OSBinaries/Csc.yml

---
Name: Csc.exe
Description: Binary file used by .NET Framework to compile C# code
Author: Oddvar Moe
Created: 2018-05-25
Commands:
  - Command: csc.exe -out:{PATH:.exe} {PATH:.cs}
    Description: Use csc.exe to compile C# code, targeting the .NET Framework, stored in the specified .cs file and output the compiled version to the specified .exe path.
    Usecase: Compile attacker code on system. Bypass defensive counter measures.
    Category: Compile
    Privileges: User
    MitreID: T1127
    OperatingSystem: Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11
  - Command: csc -target:library {PATH:.cs}
    Description: Use csc.exe to compile C# code, targeting the .NET Framework, stored in the specified .cs file and output the compiled version to a DLL file with the same name.
    Usecase: Compile attacker code on system. Bypass defensive counter measures.
    Category: Compile
    Privileges: User
    MitreID: T1127
    OperatingSystem: Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11
Full_Path:
  - Path: C:\Windows\Microsoft.NET\Framework\v4.0.30319\Csc.exe
  - Path: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Csc.exe
  - Path: C:\Windows\Microsoft.NET\Framework\v3.5\csc.exe
  - Path: C:\Windows\Microsoft.NET\Framework64\v3.5\csc.exe
  - Path: C:\Windows\Microsoft.NET\Framework\v2.0.50727\csc.exe
  - Path: C:\Windows\Microsoft.NET\Framework64\v2.0.50727\csc.exe
Detection:
  - Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/process_creation/proc_creation_win_csc_susp_parent.yml
  - Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/process_creation/proc_creation_win_csc_susp_folder.yml
  - Elastic: https://github.com/elastic/detection-rules/blob/61afb1c1c0c3f50637b1bb194f3e6fb09f476e50/rules/windows/defense_evasion_dotnet_compiler_parent_process.toml
  - Elastic: https://github.com/elastic/detection-rules/blob/82ec6ac1eeb62a1383792719a1943b551264ed16/rules/windows/defense_evasion_execution_msbuild_started_unusal_process.toml
  - IOC: Csc.exe should normally not run as System account unless it is used for development.
Resources:
  - Link: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-options/